Infrared spectroscopy is when an instrument uses infrared radiation to detect through "mechanical sight" things that may be difficult to see in other spectra. For instance, hydrocarbons can be detected through infrared spectroscopy. While using this process has a number of advantages, it also has some disadvantages.
One of the primary advantages is that infrared spectroscopy causes no damage. Several other forms of mechanical sight can detect particles through other spectra, but many of their methods use radiation. For example, X-ray technology requires precautions so that the radiation doesn't cause damage to people in the area. However, infrared radiation is harmless and won't damage the environment or the area being viewed.
One downside of using infrared spectroscopy is that it requires very sensitive and properly tuned instruments. Any basic infrared instrument can see the infrared spectrum, but being able to focus on it well enough to make sense of what's being seen requires tools that are well tuned. Also, the better tuned and focused a set of tools happens to be, the more expensive it will be to buy and maintain in the long term.
A major advantage of infrared spectroscopy is that the samples being viewed don't require any sort of special preparation. Some tests may require a subject to be bathed in radiation or have radioactive dye put into it, but infrared spectroscopy doesn't require that. The detection instruments simply need to be set up so they can "look" at the subject. The readings can be taken without doing anything special to the subject at hand.